#43: implemented drop schema logic

pom.xml

@@ -3,7 +3,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.exasol</groupId>
   <artifactId>sql-statement-builder</artifactId>
-  <version>1.0.0</version>
+  <version>1.1.0</version>
   <name>Exasol SQL Statement Builder</name>
   <description>This module provides a Builder for SQL statements that helps creating the correct structure and validates variable parts of the statements.</description>
   <url>https://github.com/exasol/sql-statement-builder</url>

src/main/java/com/exasol/sql/StatementFactory.java

@@ -2,6 +2,7 @@
 
 import com.exasol.sql.ddl.create.CreateSchema;
 import com.exasol.sql.ddl.create.CreateTable;
+import com.exasol.sql.ddl.drop.DropSchema;
 import com.exasol.sql.ddl.drop.DropTable;
 import com.exasol.sql.dml.Insert;
 import com.exasol.sql.dql.Select;
@@ -76,4 +77,14 @@ public CreateSchema createSchema(String schemaName) {
     public DropTable dropTable(final String tableName) {
         return new DropTable(tableName);
     }
+
+    /**
+     * Create a {@link DropSchema} statement
+     *
+     * @param schemaName name of the schema to drop
+     * @return a new instance of a {@link DropSchema} statement
+     */
+    public DropSchema dropSchema(String schemaName) {
+        return new DropSchema(schemaName);
+    }
 }

src/main/java/com/exasol/sql/ddl/Schema.java

@@ -3,6 +3,7 @@
 import com.exasol.sql.AbstractFragment;
 import com.exasol.sql.Fragment;
 import com.exasol.sql.ddl.create.CreateSchemaVisitor;
+import com.exasol.sql.ddl.drop.DropSchemaVisitor;
 
 /**
  * This class represents a {@link Schema} in an SQL Statement
@@ -33,4 +34,8 @@ public String getName() {
     public void accept(CreateSchemaVisitor visitor) {
         visitor.visit(this);
     }
+
+    public void accept(DropSchemaVisitor visitor) {
+        visitor.visit(this);
+    }
 }

src/main/java/com/exasol/sql/ddl/create/rendering/CreateSchemaRenderer.java

@@ -22,7 +22,7 @@ public CreateSchemaRenderer(final StringRendererConfig config) {
     /**
      * Create an {@link CreateSchemaRenderer} using the default renderer configuration
      *
-     * @return insert renderer
+     * @return CREATE SCHEMA renderer
      */
     public static CreateSchemaRenderer create() {
         return new CreateSchemaRenderer(StringRendererConfig.createDefault());
@@ -32,7 +32,7 @@ public static CreateSchemaRenderer create() {
      * Create an {@link CreateSchemaRenderer}
      *
      * @param config renderer configuration
-     * @return create schema renderer
+     * @return CREATE SCHEMA renderer
      */
     public static CreateSchemaRenderer create(final StringRendererConfig config) {
         return new CreateSchemaRenderer(config);

src/main/java/com/exasol/sql/ddl/create/rendering/CreateTableRenderer.java

@@ -23,7 +23,7 @@ public CreateTableRenderer(final StringRendererConfig config) {
     /**
      * Create an {@link CreateTableRenderer} using the default renderer configuration
      *
-     * @return insert renderer
+     * @return CREATE TABLE renderer
      */
     public static CreateTableRenderer create() {
         return new CreateTableRenderer(StringRendererConfig.createDefault());
@@ -33,7 +33,7 @@ public static CreateTableRenderer create() {
      * Create an {@link CreateTableRenderer}
      *
      * @param config renderer configuration
-     * @return create table renderer
+     * @return CREATE TABLE renderer
      */
     public static CreateTableRenderer create(final StringRendererConfig config) {
         return new CreateTableRenderer(config);

src/main/java/com/exasol/sql/ddl/drop/Cascade.java

@@ -0,0 +1,23 @@
+package com.exasol.sql.ddl.drop;
+
+import com.exasol.sql.AbstractFragment;
+import com.exasol.sql.Fragment;
+
+/**
+ * This class represents CASCADE clause in DROP SCHEMA SQL statement
+ */
+public final class Cascade extends AbstractFragment implements DropSchemaFragment {
+    /**
+     * Create an instance of {@link Cascade} class
+     *
+     * @param root root SQL statement this fragment belongs to
+     */
+    protected Cascade(final Fragment root) {
+        super(root);
+    }
+
+    @Override
+    public void accept(final DropSchemaVisitor visitor) {
+        visitor.visit(this);
+    }
+}

src/main/java/com/exasol/sql/ddl/drop/CascadeConstraints.java

@@ -4,7 +4,7 @@
 import com.exasol.sql.Fragment;
 
 /**
- * This class represents "cascade constraints" expression in DROP TABLE SQL statement
+ * This class represents CASCADE CONSTRAINTS clause in DROP TABLE SQL statement
  */
 public final class CascadeConstraints extends AbstractFragment implements DropTableFragment {
     /**

src/main/java/com/exasol/sql/ddl/drop/DropSchema.java

@@ -0,0 +1,104 @@
+package com.exasol.sql.ddl.drop;
+
+import com.exasol.sql.AbstractFragment;
+import com.exasol.sql.SqlStatement;
+import com.exasol.sql.ddl.Schema;
+
+/**
+ * This class implements an SQL {@link DropSchema} statement
+ */
+public class DropSchema extends AbstractFragment implements SqlStatement, DropSchemaFragment {
+    private Schema schema;
+    private Cascade cascade;
+    private Restrict restrict;
+    private boolean ifExists = false;
+
+    /**
+     * Create a new instance of an {@link DropSchema} statement
+     *
+     * @param schemaName name of the table to drop
+     */
+    public DropSchema(final String schemaName) {
+        super(null);
+        this.schema = new Schema(this, schemaName);
+    }
+
+    /**
+     * Add IF EXISTS clause into a DROP SCHEMA statement
+     *
+     * @return <code>this</code> for fluent programming
+     */
+    public synchronized DropSchema ifExists() {
+        if (!this.ifExists) {
+            this.ifExists = true;
+        }
+        return this;
+    }
+
+    /**
+     * Add CASCADE clause into a DROP SCHEMA statement
+     *
+     * @return <code>this</code> for fluent programming
+     */
+    public synchronized DropSchema cascade() {
+        cascade = new Cascade(this);
+        return this;
+    }
+
+    /**
+     * Add RESTRICT clause into a DROP SCHEMA statement
+     *
+     * @return <code>this</code> for fluent programming
+     */
+    public synchronized DropSchema restrict() {
+        restrict = new Restrict(this);
+        return this;
+    }
+
+    /**
+     * Get a schema name
+     *
+     * @return schema name
+     */
+    public String getSchemaName() {
+        return schema.getName();
+    }
+
+    public Cascade getCascade() {
+        return cascade;
+    }
+
+    public Restrict getRestrict() {
+        return restrict;
+    }
+
+    @Override
+    public void accept(DropSchemaVisitor visitor) {
+        validateCascadeAndRestrict();
+        visitor.visit(this);
+        this.schema.accept(visitor);
+        if (cascade != null) {
+            cascade.accept(visitor);
+        }
+        if (restrict != null) {
+            restrict.accept(visitor);
+        }
+    }
+
+    /**
+     * Get true when IF EXISTS clause presents
+     *
+     * @return if exists
+     */
+    public boolean getIfExists() {
+        return ifExists;
+    }
+
+    private void validateCascadeAndRestrict() {
+        if (cascade != null && restrict != null) {
+            throw new IllegalArgumentException(
+                  "DROP SCHEMA expression must not contain CASCADE and RESTRICT clauses at the came time. "
+                        + "Use only one of them.");
+        }
+    }
+}

src/main/java/com/exasol/sql/ddl/drop/DropSchemaFragment.java

@@ -0,0 +1,15 @@
+package com.exasol.sql.ddl.drop;
+
+import com.exasol.sql.Fragment;
+
+/**
+ * This is the common interface for all fragments of a DROP SCHEMA statement.
+ */
+public interface DropSchemaFragment extends Fragment {
+    /**
+     * Accept a visitor (e.g. a renderer or validator)
+     *
+     * @param visitor visitor to accept
+     */
+    public void accept(DropSchemaVisitor visitor);
+}

src/main/java/com/exasol/sql/ddl/drop/DropSchemaVisitor.java

@@ -0,0 +1,13 @@
+package com.exasol.sql.ddl.drop;
+
+import com.exasol.sql.ddl.Schema;
+
+public interface DropSchemaVisitor {
+    public void visit(DropSchema dropSchema);
+
+    public void visit(Schema schema);
+
+    public void visit(Cascade cascade);
+
+    public void visit(Restrict restrict);
+}

src/main/java/com/exasol/sql/ddl/drop/DropTable.java

@@ -30,7 +30,7 @@ public void accept(final DropTableVisitor visitor) {
     }
 
     /**
-     * Add "if exists" expression into a DROP TABLE statement
+     * Add IF EXISTS clause into a DROP TABLE statement
      *
      * @return <code>this</code> for fluent programming
      */
@@ -42,7 +42,7 @@ public synchronized DropTable ifExists() {
     }
 
     /**
-     * Add "cascade constraints" expression into a DROP TABLE statement
+     * Add CASCADE CONSTRAINTS clause into a DROP TABLE statement
      *
      * @return <code>this</code> for fluent programming
      */
@@ -52,7 +52,7 @@ public DropTable cascadeConstraints() {
     }
 
     /**
-     * Get true when "if exists" expression presents
+     * Get true when IF EXISTS clause presents
      *
      * @return if exists
      */

src/main/java/com/exasol/sql/ddl/drop/Restrict.java

@@ -0,0 +1,23 @@
+package com.exasol.sql.ddl.drop;
+
+import com.exasol.sql.AbstractFragment;
+import com.exasol.sql.Fragment;
+
+/**
+ * This class represents RESTRICT clause in DROP SCHEMA SQL statement
+ */
+public final class Restrict extends AbstractFragment implements DropSchemaFragment {
+    /**
+     * Create an instance of {@link Restrict} class
+     *
+     * @param root root SQL statement this fragment belongs to
+     */
+    protected Restrict(final Fragment root) {
+        super(root);
+    }
+
+    @Override
+    public void accept(final DropSchemaVisitor visitor) {
+        visitor.visit(this);
+    }
+}

src/main/java/com/exasol/sql/ddl/drop/rendering/DropSchemaRenderer.java

@@ -0,0 +1,66 @@
+package com.exasol.sql.ddl.drop.rendering;
+
+import com.exasol.sql.ddl.Schema;
+import com.exasol.sql.ddl.drop.*;
+import com.exasol.sql.rendering.AbstractFragmentRenderer;
+import com.exasol.sql.rendering.StringRendererConfig;
+
+/**
+ * The {@link DropSchemaRenderer} turns SQL statement structures in to SQL strings.
+ */
+public class DropSchemaRenderer extends AbstractFragmentRenderer implements DropSchemaVisitor {
+    /**
+     * Create a new {@link DropSchemaRenderer} with custom render settings.
+     *
+     * @param config render configuration settings
+     */
+    public DropSchemaRenderer(final StringRendererConfig config) {
+        super(config);
+    }
+
+    /**
+     * Create an {@link DropSchemaRenderer} using the default renderer configuration
+     *
+     * @return DROP SCHEMA renderer
+     */
+    public static DropSchemaRenderer create() {
+        return new DropSchemaRenderer(StringRendererConfig.createDefault());
+    }
+
+    /**
+     * Create an {@link DropSchemaRenderer}
+     *
+     * @param config renderer configuration
+     * @return DROP SCHEMA renderer
+     */
+    public static DropSchemaRenderer create(final StringRendererConfig config) {
+        return new DropSchemaRenderer(config);
+    }
+
+    @Override
+    public void visit(DropSchema dropSchema) {
+        appendKeyWord("DROP SCHEMA ");
+        if (dropSchema.getIfExists()) {
+            appendKeyWord("IF EXISTS ");
+        }
+        setLastVisited(dropSchema);
+    }
+
+    @Override
+    public void visit(Schema schema) {
+        appendAutoQuoted(schema.getName());
+        setLastVisited(schema);
+    }
+
+    @Override
+    public void visit(Cascade cascade) {
+        appendKeyWord(" CASCADE");
+        setLastVisited(cascade);
+    }
+
+    @Override
+    public void visit(Restrict restrict) {
+        appendKeyWord(" RESTRICT");
+        setLastVisited(restrict);
+    }
+}

src/main/java/com/exasol/sql/ddl/drop/rendering/DropTableRenderer.java

@@ -21,7 +21,7 @@ public DropTableRenderer(final StringRendererConfig config) {
     /**
      * Create an {@link DropTableRenderer} using the default renderer configuration
      *
-     * @return insert renderer
+     * @return DROP TABLE renderer
      */
     public static DropTableRenderer create() {
         return new DropTableRenderer(StringRendererConfig.createDefault());
@@ -31,7 +31,7 @@ public static DropTableRenderer create() {
      * Create an {@link DropTableRenderer}
      *
      * @param config renderer configuration
-     * @return create table renderer
+     * @return DROP TABLE renderer
      */
     public static DropTableRenderer create(final StringRendererConfig config) {
         return new DropTableRenderer(config);